Szydlowski



April 14, 1964' J. SZYDLOWSKI 3,128,939

AXIAL-FLOW COMPRESSORS Filed July 19, 1960 United States Patent O F3,128,939 AXIAL-FLOW COMPRESSORS Joseph Szydlowslri, Usines Turbomeca,Bordes, France Filed July 19, 1960, Ser. No. 43,750 Claims priority,application France Feb. 3, 1960 8 Claims. (Q1. 230-134) The presentinvention relates to improvements in the wheels of axial-flowcompressors, and more particularly of such compressors which operate atultrasonic and supersonic speeds and comprise a wheel or wheels equippedwith blades the camber-line of which is curved in opposite directions atthe tip and at the root thereof, such as described in the applicants US.Patent No. 2,915,238. Such axial-flow compressors operate withacceptable efficiencies when the Mach number of their flow speed at thetip of the blades is high.

The present invention has for main object to provide means forincreasing such efficiencies for equal Mach numbers with respect tothose of said axial-flow compressors while permitting the obtention ofacceptable efliciencies for higher Mach numbers.

For this purpose, according to the invention, at least one cross-sectionof the blade and more particularly the cross-section at the tip of theblade has a profile with two successive opposed curvatures while thecross-section at the root has a profile with a single curvature. It isthus possible to obtain an increasing in efficiency rang ing from 3% to4% with respect to the compressors described in the aforementioned US.patent.

A further object of the invention is to provide jet engines, gas turbineengines and other similar machines, more particularly aviation machines,with compressors having rotor wheels of the type specified above.

Conveniently, an axial-flow wheel such as specified above is used as thesingle wheel of a compressor or as the first stage wheel of amulti-stage compressor, or as the single or first stage Wheel of thelow-pressure compressor of a jet engine, a double-flow jet engine orother similar machines having more than one compressor.

The invention will be better understood and other features thereof willappear by means of the following description of a practical embodimentof the invention, reference being made to the accompanying drawings, inwhich:

FIG. 1 is a perspective view of an axial-flow compressnr wheelconstructed according to the invention.

FIG. 2 is a radial view of a blade.

FIG. 3 is a partial developed view of a cylindrical section of the wheeladjacent the blade roots along the line IIIIII shown in FIG. 1.

FIG. 4 is a partial developed view of a cylindrical section of the wheeladjacent the blade tips along the line IVIV shown in FIG. 1.

FIG. 5 is a view similar to that of FIG. 2 for a modification of theblade shown in said FIG. 2.

Referring to FIG. 1, a compressor Wheel 2 is provided with a pluralityof blades 1. The centers c3 and c4 of the cross-section 3 and 4 of eachblade (FIGS. 3 and 4) through planes parallel to the plane tangent tothe rotor at the blade root and passing through the lines III-III andIVIV of FIG. 1 are substantially aligned from the blade root to theblade tip along the radius passing through the center c3 of the bladefoot.

Each blade 1 has a trailing edge 6 and a leading edge 5 which curve inopposite directions, the trailing edge 6 having a spanwise curvaturefrom the radial inner end of the blade to its radial outer end in acounter rotating direction with respect to the direction of rotation Fof the wheel while the leading edge 5 has a spanwise curvature in saiddirection of rotation. Such curvatures are so determined that the bladeis flared at its tip.

3,128,939 Patented Apr. 14, 1964 As illustrated in FIGS. 3 and 4, thechordal pitches p3 and p4 of the cross-sections 3 and 4 numericallydecreases from a positive value p3 from the root to a positive value p4at the tip of the blade, whereby the chord 78 of the cross-section 3 atthe blade root is slightly inclined to the axis of rotation A of thewheel 2 in the direction F of the wheel rotation. The chords of thesuccessive cross-section from the blade root to the blade tip are moreand more inclined to said axis so that the chord 910 of thecross-section 4 at the blade tip forms a substantially greater anglewith said axis A than does the cross-section at the root.

At the blade root the cross-section has a single curvature and aconcave-convex shape, the concave curve C being on the pressure side ofthe blade and the convex curve on the back side thereof. Near the bladetip the cross-section has a configuration with two successive opposedcurvatures. The curve C, on the pressure side of the blade comprises,close to the leading edge 5, a convex curve portion C and close to thetrailing edge 6 a concave curve portion C The curve on the back side ofthe blade near the blade tip has a concave portion close to the leadingedge and a convex portion close to the trailing edge. The center ofcurvature 0 of the concave curve C is located with respect to the bladesections in the direction F of the wheel rotation as well as the centerof curvature 0 of the concave curve portion C close to the trailing edgeof the blade. On the contrary the center of curvature 0 of the convexcurve portion C close to the leading edge of the blade is directed inthe direction opposite to said direction F. The intermediatecross-sections of the blade change progressively from the singlecurvature cross-section C to the twin-curvature cross-section C The tipof the blade is located in a plane substantially parallel to the planetangent to the body at the blade root and has an outline similar to thatof said twin-curvature cross-section C The Wheel of an axial-flowcompressor provided with blades of the character described has anincreasing in efficiency ranging from 3% to 4%, with respect to that ofa compressor according to the aforesaid US. patent, other things beingthe same.

Conveniently, the compressor wheel of the invention is more particularlyused with advantage in double flow jet engines and in jet engines of thetype described in the following US. patents in the name of applicant,No. 2,397,060, No. 2,795,372 and No. 2,922,278, in the US. patentapplication in the name of applicant Ser. No. 653,148 filed April 16,1957, now abandoned and corresponding to the French Patent No. 1,012,233patented April 9, 1952 or in the following French patents in the name ofapplicant: No. 907,666 patented July 9, 1945, No. 908,121 patentedAugust 13, 1945, No. 915,552 patented July 22, 1946, No. 1,046,175patented July 8, 1953 and No. 1,107,179 patented August 3, 1955.

Of course modifications may be made to the described embodiment withoutdeparting from the scope of the invention as defined in the appendedclaims. Thus, for example and as illustrated in FIG. 5, the curveportions C and C forming the curve C, with a twin-curvature instead ofbeing joined together tangentially may be united by a rectilinearportion 11 which is tangent to both curve portions C and C What I claimis:

1. A wheel for an axial flow compressor adapted for operating atultrasonic and supersonic speeds, said wheel comprising: a body adaptedfor rotation about an axis, and a plurality of blades supported on saidbody, said blades having a root at the location where said bladescontact said body and a remote tip, said blades also having leading andtrailing edges, each blade in crosssections in planes parallel to aplane tangent to the body at the blade root having centers which aresubstantially aligned from the blade root to the blade tip along aradial line, said blades each having a chordal pitch which uniformlydecreases from a relatively large positive value at the root of theblade to a relatively small positive value at the tip of the blade, saidcross-sections of each blade progressively varying in outline as viewedfrom a pressure side of the blade from a concave curve at the root ofthe blade to a curve having successive convex and concave portions atthe blade tip, said convex and concave portions being respectivelydisposed adjacent the leading and trailing edges.

2. A wheel as claimed in claim 1 wherein the trailing edge of each bladehas a spanwise curvature from the radial inner end to the radial outerend of the blade in a counter rotating direction with respect to therotary direction of the wheel while the leading edge of the blade has aspanwise curvature in said rotary direction, said curvatures beingsutficient to cause the blade to be flared at the tip thereof.

3. A wheel as claimed in claim 1 wherein the crosssections of each bladeat the root is concave on the pressure side of the blade and convex onthe other side of the blade and said cross-sections vary to a shape atthe tip respectively having on pressure and back sides convex-concaveand concave-convex outlines.

4. A wheel for an axial-flow compressor adapted for operating atultrasonic and supersonic speeds, said wheel comprising: a body, saidbody being adapted for rotation about an axis, and a plurality of bladessupported at the roots thereof to said body and having a remote tip,said blades further having leading and trailing edges, the trailing edgeof each blade having a spanwise curvature from the root to the tip in acounter-rotating direction relative to the rotary direction of thewheel, while the leading edge has a spanwise curvature in said rotarydirection, said curvatures being suflicient to cause the blades to beflared at the tips thereof, the centers of the cross-sections of eachblade in planes parallel to a plane tangent to the rotor at the bladeroot being substantially aligned from the blade root to the blade tipalong a radial line passing through the center of the blade root, saidblades having a chordal pitch numerically decreasing from a relativelylarge positive value at the root to a relatively small positive value atthe tip of the blade while the outline of said cross-sectionsprogressively vary on the pressure side from a concave curve at theblade root to a curve having successive convex and concave portions atthe blade tip, said convex and concave portions being respectivelydisposed close to the leading and trailing edges.

5. An axial compressor having at least one stage with at least one wheeland intended for operation at ultrasonic and supersonic speeds, at leastone of the wheels of at least one stage of the compressor includingblades supported at the roots thereof on said one Wheel, said bladeshaving leading and trailing edges, the centers of the cross-sections ofeach blade in planes parallel to a plane tangent to the wheel at theblade root being substantially aligned from the blade root to the bladestip along a radial line passing through the center of the blade root,said blades each having a chordal pitch of said crosssections whichnumerically decrease from a relatively large positive value at the rootto a relatively small positive value at the tip of the blade while theoutline of said cross-sections progressively vary as viewed on thepressure side of the blade from a concave curve at the blade root to acurve having successive convex and concave portions at the blade tip,said convex and concave portions being respectively disposed close tothe leading and trailing edges.

6. A compressor comprising at least one stage operating at ultrasonicand superosnic speeds, said compressor constituting the inlet compressorof a jet engine, said compressor having at least one wheel in at leastone stage of said compressor, said wheel having a plurality of bladesincluding roots and tips and leading and trailing edges, the centers ofthe cross-sections of each blade through planes parallel to the planetangent to the wheel at the blade root being substantially aligned fromthe blade root to the blade tip along a radial line passing through thecenter of the blade root, said blades having a chordal pitch at saidcross-sections which numerically decreases from a relatively largepositive value at the root to a relatively small positive value at thetip of the blade while the outline of said cross-sections progressivelyvary as viewed from the pressure side of the blade from a concave curveat the blade root to a curve having successive convex and concaveportions of the blade tip, said convex and concave portions beingrespectively disposed close to the leading and trailing edges.

7. A compressor comprising at least one stage with at least one wheeloperating at ultrasonic and supersonic speeds and acting as low pressurecompressor for a double flow jet engine, at least one of said wheels orat least one stage of said compressor having blades including roots andtips and leading and trailing edges, the centers of the cross-esctionsof each blade through planes parallel to the plane tangent to the wheelat the blade root being substantially aligned from the blade root to theblade tip along a radial line passing through the cen ter of the bladeroot, said blade having a chordal pitch at said cross-sections whichnumerically decreases from a relatively large positive value at the rootto a relatively small positive value at the tip of the blade while theoutline of said cross-sections progressively vary as viewed from thepressure side of the blade from a concave curve at the blade root to acurve having successive convex and concave portions at the blade tip,said convex and concave portions being respectively disposed close tothe leading and trailing edges.

8. A compressor having at least one stage operating at ultrasonic andsupersonic speeds and forming the inlet compressor of a gas turbine,said compressor comprising at least one wheel forming at least one stageof said compressor and having blades including roots and tips andleading and trailing edges, the centers of the crosssections of eachblade through planes parallel to the plane tangent to the wheel at theblade root being substantially aligned from the blade root to the bladetip along a radial line passing through the center of the blade root,said blades having a chordal pitch at said crosssections whichnumerically decreases from a relatively large positive value at the rootto a relatively small positive value at the tip of the blade while theoutline of said cross-sections progressively vary as viewed from thepressure side of the blade from a concave curve at the blade root to acurve having successive convex and concave portions at the blade tip,said convex and concave portions being respectively disposed close tothe leading and trailing edges.

References Cited in the file of this patent UNITED STATES PATENTS2,269,287 Roberts Jan. 6, 1942 2,628,768 Kantrowitz Feb. 17, 19532,667,936 Clark Feb. 21, 1954 2,784,551 Karlby et al Mar. 12, 19572,915,238 Szydlowski Dec. 1, 1959 2,931,563 Eggleton Apr. 5, 19602,935,246 Roy May 3, 1960 2,955,746 Stalker Oct. 11, 1960

1. A WHEEL FOR AN AXIAL FLOW COMPRESSOR ADAPTED FOR OPERATING ATULTRASONIC AND SUPERSONIC SPEEDS, SAID WHEEL COMPRISING: A BODY ADAPTEDFOR ROTATION ABOUT AN AXIS, AND A PLURALITY OF BLADES SUPPORTED ON SAIDBODY, SAID BLADES HAVING A ROOT AT THE LOCATION WHERE SAID BLADESCONTACT SAID BODY AND A REMOTE TIP, SAID BLADES ALSO HAVING LEADING ANDTRAILING EDGES, EACH BLADE IN CROSSSECTIONS IN PLANES PARALLEL TO APLANE TANGENT TO THE BODY AT THE BLADE ROOT HAVING CENTERS WHICH ARESUBSTANTIALLY ALIGNED FROM THE BLADE ROOT TO THE BLADE TIP ALONG ARADIAL LINE, SAID BLADES EACH HAVING A CHORDAL PITCH WHICH UNIFORMLYDECREASES FROM A RELATIVELY LARGE POSITIVE VALUE AT THE ROOT OF THEBLADE TO A RELATIVELY SMALL POSITIVE VALUE AT THE TIP OF THE BLADE, SAIDCROSS-SECTIONS OF EACH BLADE PROGRESSIVELY VARYING IN OUTLINE AS VIEWEDFROM A PRESSURE SIDE OF THE BLADE FROM A CONCAVE CURVE AT THE ROOT OFTHE BLADE TO A CURVE HAVING SUCCESSIVE CONVEX AND CONCAVE PORTIONS ATTHE BLADE TIP, SAID CONVEX AND CONCAVE PORTIONS BEING RESPECTIVELYDISPOSED ADJACENT THE LEADING AND TRAILING EDGES.